Hi, I'm a new AE Ph.D. student in the field of supersonic mixing and combustion, currently making preparations for ordering equipment necessary to perform Filtered Rayleigh Scattering measurements in our tunnel. At this point, I am implementing a model for predicting the shape of the absorption spectrum of the iodine notch filter used in the method for different filter lengths and iodine number densities. However, as I have absolutely no background in spectroscopy or quantum mechanics, understanding and implementing the model has been a bit of a bumpy road, though I believe I am nearly finished. The point where I am stuck now is in adding the contribution of the hyperfine splitting, as I don't understand how to calculate a few of the relevant parameters. A snippet of the text (Forkey, 1997) can be seen here, which shows the values which I need to calculate. This is an excerpt of the paper which supplies spectroscopic constants that I have available to me. Of course, I also have the relevant low and high rotational and vibrational quantum numbers for each rovibrational transition being considered. I've attempted to calculate G(v'), E_r(v', J') and E(v') using the (low order, it seems) estimations found here (pdf warning), though I wasn't having any luck. If anyone could help me understand how to calculate the required values using these constants, or point me to a good source which would explain it, I'd really appreciate it. Thanks in advance.